Piston or plunger for engines, pumps, and the like



' C. S. OVER April 23, 1940.

PISTON 0R PLUNGER FOR ENGINES, PUMPS, AND THE LIKE- Filed July 1, 1938 IN VENTORv C". S OVER Y ATTvs;

Patented Apr. 23, 1940 UNITED STATES PISTON on PLUNGER FOR ENGINES, PUMPS,

AND THE L Claude Stanley Over, Auckland, New Zealand IKE Application July 1, 1938, Serial No. 217,063 In New Zealand July 5, 1937 3 Claims.

This invention has reference more particularly to a new construction of piston designed for use in respect of internal combustion engines, but useful also in respect of other types of engines.

The features of construction also are suchas may with advantage be associated with the plunger of a reciprocating pump.

The invention has particular reference to that well known type of piston such as used in connection with internal combustion engines, in which the inner end of the piston is made hollow and has the end of the connecting rod placed within it and held therein by articulation upon a gudgeon pin. The part of the piston surrounding the connecting rod is generally known as the skirt and in describing the invention, this term will hereinafter be used when referring to that part.

The object of the invention is to provide a piston construction which will result in the piston surface automatically making close contact with the cylinder wall under all conditions of temperature by accommodation to the variations brought about by expansion and contraction of the piston and cylinder, and will maintain this close fit and contact with the wearing of the cylinder wall and piston surface, even if such wear is unevenly distributed. The improved construction also provides for a better distribution of lubricating oil between the piston and cylinder walls in the working of the engine.

The invention consists broadlyin the formation of the skirt portion of the piston, from a point slightly within the inmost ring, of a diameter taperingly increasing to a diameter at its inner end somewhat in excess of. the diameter of its cylinder, and with a number of slots in the skirt extending longitudinally therein, preferably in a helical fashion. This, therefore, necessitates the compression of the skirt in order that the piston may enter the cylinder and for its resilient expansion to make a close fit within the cylinder and then by reason of the presence of the slots, will permit of expansion and contraction to accommodate for variations brought about by temperature and other conditions. The slots will, in addition, provide for the distribution of the lubricating oil upon the cylinder wall and the removal of surplus oil.

The manner of giving eifect to the invention is illustrated in the accompanying drawing, in which Figure 1 is an elevation of a piston made in accordance herewith, with the slots in their simplest form.

Figure 2 is a similar elevation of a piston, in which the slots are made in an alternative form.

Figure 3 is a sectional elevation of the piston shown in Figure 2.

Figure 4 is an elevation of a piston made in an alternative manner.

Figures 5 and 6 are enlarged sectional detail views of alternative forms of the piston skirt slots.

Figure 7 is a view, on an enlarged scale, illustrating a detail in the pistons construction that will be hereinafter more fully referred to.

In giving efiect to the invention the piston A is made generally of the known form with a closed head end and a skirt portion B surrounding the hollow within which the piston rod end is articulated. The head end of the piston is made of the usual working fit for the cylinder concerned and is provided with the ordinary rings 0 characteristic of these pistons. The skirt portion, however, is made so that its external periphery taperingly increases in diameter from just within the head end to its outer end, the amount of taper being very slight.

This skirt is made with a number of narrow slots D extending generally in lines longitudinal with the piston, but preferably in the helically curving lines shown in the drawing. Sufficient of these slots are formed and made of such a width that the skirt is capable of compression in its diameter in order that it may fit within its cylinder and by its resilient expansion make the close fit, with wear compensating properties, be-. fore referred to.

The edges of the slots D also serve to scrape the inside surface of the cylinder bore and to distribute the usual lubricating oil over such surface. To aid this function of the slots, each one may be shaped as shown in Figures 2, 3 and 6, to cause the inner edge to be sharp, while the outer edge is chamfered or bevelled as at E. The chamfered edge is pierced with holes F at intervals along it. The top or sharp edge will slide freely on the inward stroke over the film of oil on the cylinder wall, and on the outward stroke, will scrape the surplus oil from the walls, returning it to the sump by medium of the chamfered perforated lower edge E. Or, each slot may be shaped as shown in Figure 5, with both edges chamfered or bevelled on the inner face of the skirt, to thus form sharp inner and outer slot edges upon the outside of the piston, for

scraping the excess or unnecessary oil from the m cylinder wall in both directions of the pistons travel, and returning such oil to the crank chamber. This form of construction saves the drilling of drain holes.

It is desirable that for the purposes of strengthening the piston, its inner end should be more or less of a rigid nature, while still retaining the tension requisite for the expansion and contraction of the skirt. For this purpose, each slot D, as it approaches the inner end of the piston skirt, may be narrowed down and then given a reverse angle, as shown at D in Figures 1 and 2, to thus provide an interlocking action between the slot edges, which will result in a compact skirt end. It is preferred, however, that the angle of the reversed end D of each slot should be more acute than that shown in the full lines of the drawing, that is, of approximately the angle indicated by the dotted lines, as thereby a more effective locking of one edge with the other is obtained. This particular shaping of the slot prevents lateral, but permits longitudinal, expansion. Or, in some cases, as shown in Figure 4, the slots may be caused to end a distance from the inner end of the piston skirt, leaving a solid ring at this end, which, however, will be of a decreased diameter to fitthe cylinder with clearance. In some cases, also, the slot may be locked at intervals in its length so that it follows a zig-zag formation.

It is also preferred that in respect of. this piston, the usual oil distributing holes G in the oil ring groove at the upper end of the skirt portion should be made to slope upwards and outwards through the skirt, instead of extending radially, as is the usual custom, as shown in Figure 3, but in more correct detail in the enlarged view Figure 7. By this formation a more eifective means of returning the oil to the crank case is provided.

It will be clear that while the features of construction herein referred to, have been described in their relation to a piston for an internal combustion engine, they may be, with some advan tages, used in respect of the pistons of other classes of engines, or in respect of the plungers of d'iiferent types of pumps.

I claim:

1. A piston of the hollow type, comprising a head, and a skirt portion extending from the inner side. of the head, said skirt portion increasing in diameter from the head to its outer end and being provided with slots cut therein and shaped to extend in a general helical manner longitudinally in the skirt, each slot being narrowed down in width near the outer end of the skirt and continued at a reverse angle to the skirt end.

2; A piston in accordance with claim 1, in which each of the said slots is shaped with a beveled outer edge upon the external peripheral surface of the'skirt and in which this edge is pierced with .holes at intervals apart along it.

3. A piston in accordance with claim 1, in which each of the said slots is upon the inside of the skirt formed with outwardly bevelled edges.

CLAUDE STANLEY OVER. 

